U.S. Pat. No. 6,679,780 discloses a cubic building block formed from a plurality of connected frame portions having a predetermined thickness. The building block is provided at each side with a cross-shaped rib portion having a thickness smaller than that of the frame portion, so that a space enclosed in each frame portion is divided into four squared cavities. The building block is also provided in the frame portion on at least one side thereof with two diagonally opposite round connecting posts, so that the two round connecting posts respectively have a center just located at a center of a corresponding square cavity on any other side of the building block, and a diameter equal to each side of the squared cavity. When any two of the above-described building blocks are vertically or horizontally juxtaposed for two complete sides on the two building blocks to face each other, the round connecting posts on a first building block could always be aligned with the square cavities on another building block. Therefore, the two building blocks could always be effectively connected or stacked at two complete sides facing each other through engagement of the round connecting posts on one building block with corresponding square cavities on another one building block.
Since the building blocks disclosed in U.S. Pat. No. 6,679,780 must be connected or stacked through full contact of two complete sides on two different building blocks, only limited connecting manners could be employed and only very limited shapes could be formed from assembling of these building blocks. The building blocks of U.S. Pat. No. 6,679,780 are therefore less attractive and less competitive in the existing commercial environments.
It is therefore tried by the inventor to develop a building block to overcome the drawbacks existed in the conventional building blocks.